1. Field of the Invention
The present invention generally relates to filter cartridges for water or beverages, such as those used in water, ice-water, soda pop machines, or other beverage dispensers. Specifically, the invention is a filter assembly, for cooperation with a filter head/manifold, that includes a filter cartridge substantially comprising recyclable components. More specifically, the invention relates to a filter assembly that allows all or substantially all of the surfaces that contact liquid to be periodically removed and recycled, thereby reducing the chance of contamination from long-term use of the surfaces. The filter cartridge is substantially non-pressure bearing, except for the neck of the filter cartridge that extends to form a liquid seal with the head/manifold. A pressure vessel substantially surrounds the filter cartridge for holding and supporting the walls of the filter cartridge under liquid pressure, but the pressure vessel does not necessarily liquid-seal to the filter cartridge or the filter head/manifold.
2. Related Art
Many filter systems for water or other liquid filtration comprise a filter that cooperates with a xe2x80x9cfilter head,xe2x80x9d which term herein includes a fluid manifold, valve head, or other connection device that directs fluid to and from the filter. The filter typically seals to an internal surface of the filter head so that the liquid entering the filter head flows into the filter, through the filter, then out of the filter to an outlet port in the filter head. In the United States and Canada, water filters are typically required to contain and withstand pressures of about 500 psi without rupturing. In the United States, water systems typically operate in the range of 40-125 psi, and NSF (National Sanitation Foundation) approval ratings typically require a water filter to withstand 4 times the claimed maximum operating pressure, or typically 500 psi. In Canada, safety factors require that water filters withstand about 508 psi for one minute.
In one general type of filter system, a disposable pressure vessel connects directly to a filter head. In such a system, when the filter media inside the pressure vessel is spent, the entire pressure vessel must be discarded, including the media contained therein. Disposable pressure vessels are not easily recyclable as there are no easy means to disassemble the pressure vessel. The disposable pressure vessel outer wall is entirely pressure-bearing, that is, it may safely withstand the liquid pressure of the particular system with a large safety margin. Therefore, disposable pressure vessels are more costly to replace because they use more plastic or more expensive materials such as aluminum. Use of disposable pressure vessels is, therefore, costly in terms of filter expense and environmental impact.
In alternative filter systems, a disposable filter cartridge may be supplied inside a pressure-bearing housing that connects to the filter head. In such a system, the pressure-bearing housing typically seals to the head using o-rings or other seals and surfaces that are contacted by the liquid being filtered. When the media of the filter cartridge is spent, the filter cartridge is typically discarded and replaced with another cartridge. The conventional filter cartridge has few recyclable components, and, the few recyclable components of the cartridge, such as granular carbon contained in the cartridge, are not removable or easily accessible to a person who might want to recycle. While the filter cartridge is removed and thrown away, the thick-walled pressure vessel is reused. During use, portions of the pressure vessel come in contact with the liquid being filtered, and, therefore, the pressure vessel may become contaminated with bacteria or other unhealthy substances. Because the pressure vessel is continually reused, the contaminated portions remain in use in the filter system and can further the contamination problem in the filter system and in the liquid flowing through it.
Therefore, there is a need for an improved filter cartridge, which is substantially recyclable and which, therefore, reduces the resource and environmental created by the filter cartridge. Also, there is a need for an economical and efficient filter cartridge that is designed so that every time the filter cartridge is removed for recycling, the surfaces with the highest chance of being contaminated are also replaced. The filter assembly of the present invention fulfills these needs.
The present invention comprises a filter assembly featuring a substantially recyclable filter cartridge. The preferred cartridge includes substantially all components which are recyclable: a cartridge body, cartridge cap, media, media-support and containment pads, and center stem/tubes. The cartridge preferably, but not necessarily, includes an invented mechanism or xe2x80x9clatchxe2x80x9d for disassembly of the components of the filter cartridge so that the components may be separated and sent to appropriate recycling processes.
The invented filter assembly preferably, but not necessarily, includes a pressure-bearing xe2x80x9cpressure vesselxe2x80x9d that substantially surrounds the filter cartridge except for the protruding neck of the filter cartridge. The pressure vessel comes in close contact with the filter cartridge to safely support and reinforce the non-pressure-bearing filter cartridge, but does not necessarily seal to the cartridge. The filter cartridge neck is pressure-bearing and protrudes out from the pressure vessel to liquid-seal directly to the filter head, so that the entire outer surface of the filter cartridge is dry, that is, not contacted by liquid during filtration, and the entire outward pressure of liquid relative to the atmosphere is directed against the interior walls of the filter cartridge. This liquid pressure is contained inside the filter cartridge neck without reinforcement, while the liquid pressure is contained inside the filter cartridge body by virtue of the surrounding pressure vessel reinforcing the filter cartridge body wall. This is preferably accomplished by a thin-walled filter cartridge body with the neck wall being significantly thicker than the body wall, which results in excellent pressure containment and NSF Safety Factors with a much-reduced amount of total plastic to be recycled after use.
Objects of the present invention, therefore, include providing a recyclable filter cartridge for water and beverage filtration, herein including filtering, treatment, or other processing. An object is to provide such a recyclable filter cartridge that greatly reduces the environmental impact of the plastics and other materials used in the filter cartridge, and that is easily disassembled for separation of the various components for proper recycling. A further object is to make the filter cartridge recyclable while minimize the total amount of plastic that must be dealt with in the recycling process. This minimization of total recycled plastic is preferably done by providing a thin filter cartridge outer wall except for the relatively small pressure-bearing neck. Another object is to provide a filter cartridge system in which all or substantially all of the surfaces that liquid contacts after leaving the filter head and prior to returning to the filter head are removed from the system when the filter cartridge is removed for recycling. Thus, the liquid-contact surfaces are filter cartridge surfaces rather than pressure vessel surfaces, and are replaced each time the filter cartridge is replaced.